there is a valvve that lets the coolant thru the heater core when heat is selcted then when it is off it goes thru thur the return instead of the heater core i bet your car is running a little off if it is the vavle works of a vacuum line and the vavle has a crack in it

Possibly.. the actuators which operate the doors actually have a position signal for reference, but the actual motors inside the actuators dont realize there is a limit and overshoot their limits causing the fine wires inside to rip apart rendering the actuator scrap but this happens when actuators are still plugged in to the connector while being taken off the heater door, and they can and will still move with the key in the off position if the actuator thinks it not in the proper position..thats how they work anyway.hope you had them unplugged untill the last, then this would'nt happen....hope this explaination helped

You just might have an air lock. Try bleeding the system from the heater hose at the firewall. Losen one hose a little, and at operating temp. open slightly to let air out. You will lose some coolant, but just refill the rad. Now, both hoses should get hot.

You might have to purge the coolent system cause when you change stuff like that you normally have to bleed the the colent system. So what you have to do is run the car untill your temp gets to 195 degrees the cut the car off and let the coolent drain down and then refill and geep doing that untill you have heat.

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Related Questions:

Thermostat stuck open, low coolant level, stuck blend door or bad blend door actuator, or blogged heater core. Feel both hoses to the heater core. They should both be about the same temp. If one is hot and the other is cold, you have a clogged heater core. If both are hot, then the thermostat is working and you've got a blend air door/actuator problem. Actuator failure is pretty common on these. Remove the actuator and open the door by hand. If you get heat, replace the actuator

Air
Temperature Control Blend Door Failure No Heat or no AC (dependes on
where door sticks)

In
all modern cars there is a tiny DC electric motor driven gear drive
that moves a plastic door that blends heated and cooled air from the
AC and the heater core, this is called (interestedly enough) the air
temperature control blend door actuator. The motor that moves this
door fails because the door starts sticking from warping, most common
complaint is no heat but it can be no AC as well. To replace these
parts (blend door and blend door actuator) you must remove the entire
dash from the car. Always have this problem confirmed by a dealer or
qualified repair shop as it is a very expensive repair.

Other
causes of no heat in the cabin are engine thermostats that are stuck
open (engine runs cold) or air bubbles in the cooling system.

sound like a vacuum leak. you can check this by spraying wd40 very carefilly on the vacuum lines under the hood. the idle will change when a leak is detected. could also be a modulator valve or vacuum line under the dash. check this with a spray bottle filled with water. dont want the smell of wd40 in the cabin

If heater core is getting coolant circulating through it then you may have a temp blend door, or blend door actuator not working properly. The blend door is located in the air box under the dash, and the actuator is located on the air box. You may be able to visually check the operation while turning the temp knob, by locating the coresponding actuator on the air box and monitoring the movement. If it is moving ok and still no heat then the blend door, or lever is broken, which will require removal of the dash.

there is a valvve that lets the coolant thru the heater core when heat is selcted then when it is off it goes thru thur the return instead of the heater core i bet your car is running a little off if it is the vavle works of a vacuum line and the vavle has a crack in it